In this work we study the spectral properties (3600–6800 Å)
of the nuclear region of early-type galaxies at low (),
intermediate (including surroundings of the Magellanic Clouds) and high
(South Polar Cap) Galactic latitudes. We
determine the reddening values of the galaxies by matching their continuum
distribution with respect to
those of reddening-free spectral galaxy templates with similar stellar
populations.
We also compare the spectroscopic reddening value of each galaxy
with that derived from
100 μm dust emission () in its line of sight, and we
find that there is agreement up to . Beyond this limit values are higher.
Taking into account the data up to , we derive a
calibration factor of 0.016 between the spectroscopic values
and Schlegel et al.'s ([CITE]) opacities. By combining this
result with an AK extinction map built within ten degrees of the Galactic centre
using Bulge giants as probes (Dutra et al. [CITE]), we extended the calibration of dust
emission reddening maps to low Galactic
latitudes down to and ().
According to this new calibration, a multiplicative factor of ≈0.75 must be applied to the COBE/IRAS dust emission reddening maps.

Key words: ISM: dust, extinction / Galaxy: general / galaxies: ISM

*

Based on observations made at
Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de
Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of
La Pata, Córdoba and San Juan, Argentina.

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